Things That Work

So we finally tracked down just how Jay broke Grooveshark Lite the other day.

He apparently managed to trigger a very obscure language bug, that no one has really posted about, though if you dig deep enough into Adobe’s bug tracking system, you can find some reports of, though it’s supposedly fixed as of some version of the compiler that I have no idea if it’s in production yet.

This is all it takes to break Actionscript with a nasty runtime error:

private function breakIt():void
{
    var arr:Array = [];
    for each (var obj:Object in arr) {
        switch ('s') {
            case 's':
                if (null) {
                }
            //break;
        }
    }
}

The key here is the nested for/switch/if and that the expression for the if statement evaluates to false, and that there is nothing in the case after the if.

Uncommenting the commented break statement will prevent the bug. Even a variable declaration on that line will prevent the bug. Removing the switch from inside the for loop will prevent the bug. Notice in this case the loop shouldn’t even be executing: the array is empty. Doesn’t matter, it crashes anyway.

The runtime error this triggers is “VerifyError: Error #1068: CLASSNAME and CLASSNAME cannot be reconciled.” where CLASSNAME is the name of the class that contains the above code.

So if you’re getting the above error in your code, check around for any constructs like the above.